Ex Vivo Quantification of Calcification Stiffness in Aortic Stenosis: Biomechanical Data from Resected Human Valves.

Purpose: Aortic stenosis (AS) is characterized by progressive calcification of the aortic valve. While imaging can assess the extent and localization of calcification, intraoperative findings suggest substantial variability in mechanical stiffness. Quantitative biomechanical evaluation is needed to inform optimized treatment strategies. We aimed to quantify the mechanical stiffness of calcified nodules in human AS.

Methods: We performed ex vivo compression testing on 129 calcified nodules resected from 46 patients undergoing surgical aortic valve replacement for severe AS. Stress-strain relationships were measured to characterize the mechanical behavior of the nodules, and two stiffness parameters-compression strength (CS) and compression energy (CE)-were defined. These parameters were compared with the computed tomography (CT) density of the region from which each nodule was resected.

Results: Calcified nodules exhibited wide variation in reactive stress, with maximum values in low strain regions ranging from 60 to 100-fold higher than the minimum. The stress-strain curves demonstrated three-phase pattern consisting of an initial increase, plateau phase, and steep rise in stress. The median CS increased from 0.38 MPa at 10% strain to 1.73 MPa at 50% strain, and median CE from 0.020 to 0.43 J/cm³ across the same range. The Pearson's correlation coefficients between CT density and these parameters ranged from 0.291 to 0.454.

Conclusion: Some nodules demonstrated marked reactive stress even at low strain levels, indicating strong resistance to compression with minimal deformation. This study provides reference data on the biomechanical stiffness of calcification in human AS.